Plant is looking bad

My boy gave me some plants. This is my first time really growing and he didn't really tell me exactly how often to water and how. He gave me a jug of his nutrient mixture and was like: good luck. Consequently I think I may have over-nuted them. Later he told me I should apply the nutes every third watering.

So, my plants are looking a little bad. The tips are burning badly no matter how far away the lights are. After reading through the forums and talking to a few people, I determined that the pH levels may be off. I got a pH meter. I mixed up my water and nutrients and then measured the pH. Its usually between 6.5 - 7.0. The leaves still showed the same problems. I checked the pH on the drained water and it read 5.5??? At this point i figure the soil is all messed up from over-feeding. The plant also has brown spots, which i've learned is caused by excess salt build up. Now I also notice the leaves folding upwards which from magnesium deficiency.

Strangely enough, with all of these problems, the plants are in their fourth week of flowering and still growing. I'm pretty sure this will hurt my yield though. Would it be better to take these plants out of the soil and replant in new soil, or should I try some leaching solution. Should I mix the water to maybe 7.3 before applying?

Thanks.

Strangely enough, all of these problems are also very similar to heat stress results, especially the folding of the leaves. It might be a good idea, if you're not already, to monitor your high and low temps.

I would try to change the it to soiles soil I heard it is very good for sick plantes and has lots of nutrieans

Yeah.. I think i'm gonna put them in some new soil. As for the leaves, what should I do with them? Should I clip the damaged leaves off, or should I leave them alone?